CARACAS, Feb 20 (Reuters) - Security forces faced off with demonstrators in streets blocked by burning barricades in several Venezuelan cities on Thursday in an escalation of protests against President Nicolas Maduro's socialist government, witnesses said.

At least five people have died since protests turned violent last week, with scores injured and arrested.

The demonstrators, mainly students, blame the government for violent crime, high inflation, shortages of many products and the alleged repression of opponents.

Residents in middle-class neighborhoods banged pots and pans in a traditional form of protest, and demonstrators were out again from early on Thursday.

"I declare myself in civil disobedience," read one banner held up by demonstrators spread across a Caracas road.

There were similar scenes in the western Andean states of Tachira and Merida that have been especially volatile since hardline opposition leaders called supporters onto the streets in early February demanding Maduro's departure.

In San Cristobal city, which some residents are describing as a "war zone", many businesses remained shut as students and police faced off in the streets again on Thursday.

With local TV channels not covering the unrest, Venezuelans are turning to social media to swap information and images, though falsified photos are also circulating.

Tensions have escalated since opposition leader Leopoldo Lopez, a 42-year-old Harvard-educated economist, turned himself in to troops this week. He is being held in Caracas' Ramo Verde jail and faces charges of fomenting the violence.

"Change depends on every one of us. Don't give up!" Lopez's wife Lilian Tintori said via Twitter early on Thursday.

COUP ALLEGATIONS

Maduro, who was narrowly elected last year to succeed socialist leader Hugo Chavez after his death from cancer, says Lopez and others are in league with the U.S. government and are seeking a coup.

The latest direct victim of the unrest was a college student and local beauty queen, Genesis Carmona, 22, shot in the head during a demonstration in the central city of Valencia.

In an indirectly linked death, state television channel VTV said the mother of one its employees died on Wednesday as she was being rushed to hospital in Caracas. VTV said she suffered a heart attack while the ambulance carrying her was stuck in gridlock due to opposition supporters blocking roads.

"We cannot underestimate those fascist groups whose boss is behind bars," Maduro said in a speech late on Wednesday, showing videos and photos of violence he said was being perpetrated against government supporters and buildings.

"I'm not playing with democracy. I do not accept that they challenge the Venezuelan people and our constitution."

Speaking in Mexico, U.S. President Barack Obama criticized Maduro's government for arresting protesters and urged it to focus on addressing the "legitimate grievances" of its people.

Street protests were the backdrop to a short-lived coup against Chavez in 2002 before military loyalists and supporters helped bring him back.

There is no evidence the military, which was the decisive factor in 2002, may turn on Maduro now.

Detractors call Lopez a dangerous hothead. He has frequently squabbled with fellow opposition leaders and was involved in the 2002 coup, even helping arrest a minister.

Though the majority of demonstrators have been peaceful, an increasingly prominent radical fringe has been attacking police, blocking roads and vandalizing buildings.

Rights groups say the police response has been excessive, and some detainees say they were tortured. (Additional reporting by Girish Gupta; Editing by James Dalgleish)